Precision disk grinder

ABSTRACT

A grinder for producing a precise planar surface on a workpiece, the grinder being of the general type in which the chuck carrying the workpiece and the shaft carrying the grinding wheel are rotated about axes which are perfectly parallel to one another and perfectly normal to the desired planar surface. In the grinder of the invention, a grinding system, comprising a grinder motor and a grinding wheel, is mounted on a parallelogram linkage to be movable along the rotational axis of the grinding system. A resilient actuator means urges the grinding system into grinding engagement. Preferably, the actuator means is a pneumatically cushioned hydraulic cylinder, and the pressure is adjustable to aid in adjusting to a predetermined grinding load. The actuator means is opposed by an adjustable stop. The stop may be adjusted to precisely locate the plane of application of the grinding load. Operation of the actuator against the stop aids in bringing under control the deformation and displacement occurring in the grinder during operation. In the preferred form of the invention, the stop and/ or actuator may be adjusted during the grinding operation. In a further refinement of the preferred form, the grinder includes a continuous grinding load indicating means and a timer or clock for indicating the time period of application of each grinder load stage. Production of the desired surface on the workpiece is achieved by adjustment during grinding according to a predetermined load-time program.

United States Patent Millett g 3,704,555 [45] Dec 5,1972

[54] PRECISION DISK GRINDER [72] inventor: Ray C. Millett, Costa Mesa, Calif. 13 Assignee: Marina Industries,lnc. [221 Filed: .l une o, 1971 211 Appl.No.: 151,815

[52] us. Cl ..s1/1s2 [51] lm. cl. -324 1/04 [58] Field of smell ..sl/1o9. 118,132, 126

[56] References Cited UNlTED STATES PATENTS 2,998,679 9/l96l Mattison .....5l/l09 9/1951 Davis ..5lll26 Primary Examiner l-larold Whitehead Attorney-Edmond F. Shanahan [57] ABSTRACT A grinder for producing a precise planar surface on a workpiece, the grinder being of the general type in which the chuck carrying the workpiece and the shaft carrying the grinding wheel are rotated about axes which are perfectly parallel to one another and perfectly normal to the desired planar surface. ln the grinder of the invention, a grinding system, comprising a grinder motor and a grinding wheel, is mounted on a parallelogram linkage to be movable along the rotational axis of the grinding .system.

A resilient actuator means urges the grinding system 1 into grinding engagement. Preferably, the actuator means is a pneumatically cushioned hydraulic cylinder, and the pressure is adjustable to aid in adjusting to a predetermined grinding load.

The actuator means is opposed by an adjustable stop. The stop may be adjusted to precisely locate the plane of application of the grinding load. Operation of the actuator againstthe stop aids in bringing under control the deformation'and displacement occurring in the grinder during operation.

In the preferred form of the invention, the stop and/ or actuator may be adjusted during the grinding operation. Ina further refinement of the preferred form, the grinder includes a continuous grinding load indicating meansand a timer or clock for indicating the time period of application of each grinder load stage. Production of the desired surface on the workpieceis achieved by adjustment during grinding according to a predetermined load-time program.

"Claims, 6 Drawing Figures PATENTEDHEB 5 I912 3 704. 555 SHEET 1 0F 5 .84) a MILLETT;

PATENTEUBEB 5 m2 sum u or 5 i M? a M PATENTED 5 I97? 7 3,704,555

SHEET 5 or 5 IVA/EH08 mdgaim,

PRECISION nrsx GRINDER The grinder of the present invention finds special application in grinding of flat faces on computer disks. The preferred tolerance for such disks is in the range of a few millionths of an inch, and previously known flat surface grinders are generally not reliable beyond tolerances of a few ten-thousandthsof an inch. However, the utility of the grinder extends to applying a flat surface on any kind of workpiece, in which high precision tolerances justify the use of a high precision machine of the type of this invention.

The present invention is of the general type of surface grinder in which the workpiece is rotated at high speed about a chuck axis normal to the desired planar surface, while the grinding tool is also'rotated athigh speed about a tool axis, which is likewise normal to the planar surface desired, but is located at some distance, usually a few inches, to one side of the chuck axis. The grinding tool actually grinds only an annular band disposed substantially in the plane of desired flat surface. However, more extensive flat surfaces can be produced by moving the grinding tool axis or the chuck axis through different position spacings, during the successive grinding operations.

In. the past, precision disk grinders have involved transport of the grinder or the workpiece .on a carriage moving ona set of ways. It is impossible to machine a set of ways and produce straight-line movement with the same precision and freedom from vibration, as it has been found possible to achieve with the parallelogram linkage of the invention.

In the past, the chuck has generally been rotated on a shaft driven by belting or other indirect drive means. All of these generally used means have introduced slight tendencies toward vibration, which has been acceptable in most grinding applications of the past, but

which produce minute ripples on thesurfacmSuch ripples are not acceptable in computer memory disks or the like, since they prevent the surface smoothness within the tolerance desired.

In the present invention, a parallelogram linkageis supported in highly preloaded bearings, gpreferrably tapered roller bearings, which avoid the problems encountered with a carriage transported on ways.

Moreover, minute displacements and minute deformations, which cannot be avoided in precision machines, are controlled in the present invention by combining an actuator for resiliently applying grinding load, with an adjustable stop opposing the application of grinding load. In the preferred form of theinvention, a pneumatically cushioned hydraulic cylinder is mechanically connected to the parallelogram linkage; controlled application of air to the oil supplied to the cylinder resiliently urges the parallelogram linkage, and the grinding system mounted uponit, into grinding load engagement with a workpiece mounted on a rotating chuck.

In the preferred form of the invention, movement of the parallelogram linkage into grinding P ition is opposed by a stop, which may be preciselyand continuously adjusted in position during operation of the grinder.

The grinder of the present invention is uniquely adapted to precision grinding according to a predetermined program of grinding loads and time periods. At

all times during operation, the grinding load is detected by a suitable load detection means, such as a meter measuring the current required by the grinder motor. As the grinding progresses, grinding load can be adjusted by adjustment of the adjustable stop, either continuously, or in a step-wise manner. In its preferred form, the grind includes a timer clock, indicating the time rate of grinder load change, or the time period for which a particular grinding load-has been applied. The

best combination of grinding loads and time periods may be predetermined for a given machine and a given workpiece by experimentation. Once established, the grinding load-timed program may be adjusted to maintain tolerance, as each successive workpiece is measured after grinding according to procedures well known to persons skilled in the art of precision tooling.

The'timing and extent of stop adjustment, or other controlled changes of 'thegrinder during the grinding operationmay be accomplished by a human operator observing both grinding load and timer clock; or it may be accomplished automatically by automatic devices responded to detected grinding load, and grinding step time period, the automatic device being programmed according to predetermined grinding load-timer program, by any means of the many automatic programmable means available to those skilled in the art of precision tooling.

In an important preferred form of the invention, the

parallelogram linkage has two bearings at each of its pivot axes. The spacing of the bearings laterally with respect to the central plane of parallelogram movement is sufficiently wide to permit the accommodation of the actuator, or the stop, or preferrably both, between opposite side bearings of the parallelogram linkage.

The foregoing and other objects and advantage of the invention will be understood from the following description of one preferred specific embodimentof the invention, which-description-should be read with reference to the accompanying drawings, in which:

FlG..1 is afront elevational view of the grinder of the invention, except for the chuckdriving system, which is illustrated in the digrammatic view of FIG. 5;

FIG. 2 is a right side elevational view of the grinder of FIG. I;

FIG. 3 is a perspective view of the grinder of FIGS. 1 and 2, as seen from the right rear;

FIG. 4 is a perspective view of an exploded assembly of the column and linkage which carry the grinding system of the grinder;

FIG. 5 is a diagrammatic view of the grinder and its associated instruments and controls, and

FIG. 6 is a perspective view, partly sectioned, of a grinding wheel used in the grinder of FIGS. 1-5.

A general introductory description of the invention will make reference primarily to FIGS. 1 and ,5. The particular embodiment of the grinder of the invention illustrated in the drawings is designated as a whole by thenumeral 10. A rigid, stationary base structure indicated generally by the numeral 11 (FIG. 5) is comprised principally of a chuck table 12 and a linkage support column' l3. It is preferred that column 13 be fastened to table 12 in a manner which permits some adjustment in their relative position; for example, assembly may be by bolts, as in the preferred embodiment illustrated, with one or more bolt holes in the form of straight or arcuate slots.

The principal mechanical parts of grinder are best seen in FIG. 1, whereas the associated instrumentation, and the chuck motor are best seen in the diagrammatic view of FlG. 5, as will be described hereinafter.

A transparent plastic shield 15, indicated in dashed line in FIGS. 1 and 5, encloses the upper part of grinder 10 to confine oil spattering during the grinding operation; but this oil shield is omitted in most of the drawings for purposes of illustration'clarity.

Grinder 10 contains two independently driven rotating systems, a chuck system indicated generally by the numeral 16, and a grinding system indicated generally by the numeral 17.

Grinding system 17 is vertically movable, being mounted on a parallelogram linkage 18, which swings from linkage supportcolumn 13. Although grinder 10 is illustrated with vertical rotational axes for chuck system 16 and grinding system 17, and vertical movement for grinding system 17, the invention includes within its scope grinders constructed with horizontal or oblique rotational axes. The illustrated grinder 10, however, provides a construction which is convenient for observation and operation by a human operator.

The principal parts of chuck system 16 are a chuck motor 21 and a chuck 22. Chuck motor 21 is securely mounted in table 12 immediately under a chuck-bearing wall 23. Chuck 22 is rotationally mounted in chuckbearing wall 23 by means of chuck bearing 24, and is coupled directly to the shaft 25 of chuck motor 21, without any intervening drive whatever.

Preferably, chuck 22 is of'the vacuum type. The disk, or similar workpiece, is centered on the upper chuck surface 26, and held in position by atmospheric pressure, because of a vacuum created at upper'chuck surface 26. A vacuumline 27 passes through a two-position chuck valve 28, conduit 29, rotating coupling 30, and an axial passage 31 through motor shaft 25 to chuck 22. Upper chuck surface 26 has numerous openings communicating with axial passage 31, to accomplish firm vacuum holding of a workpiece disk on upper chuck surface 26.

Preferably, chuck motor 21 is stopped by electric current reversal, and not by any braking system, since the latter might produce imperfections'in the precision grinding operation on aiworkpie'ce mounted on chuck surface 26. In the preferred form illustrated, FIG. 5, chuck motor 21 is a three-phase alternating current motor, supplied with three-phase alternating current through power line 35, reversing switch 26, and motor line 37. Reversing switch 36 starts the grinder motor 21 in grinding rotation when a microswitch 40 indicates that the grinding system 17 has been lowered into grinding position as illustrated in FIG. 5. When the grinding system '17 is retracted upwardly at the conclu sion of grinding workpiece, microswitch 40 indicates Vacuum valve 28 is a two-position valve, so that it Q can be turned to a pressure-supply position, at the conclusion of the grinding operation, to supply pressure from pressure line 45, through the line 29, the axial passage 31, and the openings inupper chuck surface 26, to free the workpiece disk from the chuck 22 by pressure, so that the operator can-remove the workpiece with facility.

In FIG.-1, a workpiece 50 is seenas its upper surface is undergoing grinding. The vacuum openings 26a are seen in dashed outline.

Grinding system 17 is seen tob'e comprised principally of a grinder motor 51, and a grinding wheel 52 which is typically 'of a construction illustrated in detail in the partially sectioned perspective view of FIG. 6. Grinding'wheel 52 has a step 53 for mounting directly on the shaft of grinder motor 51. At its opposite end, the grinding wheel 52 has an annular grinding surface 54 which is rotated in grinding engagement with the surface of workpiece disk 50 as'seen in FIG. 1. As in the case of the chuck system 16, it is important in the grinder system 17 that grinding wheel 52 rotate integrally with the shaft of grinding motor 51, without any intervening drive. Also, in this connection, the entire grinding system 17 is preferably carried as a unit on the parallelogram linkage 18, and is movable upwards and downwards along a vertical line indicated by the doubleheaded arrow 56, in FIG. 1. Preferably, grinder motor 51 is of a type which can be speed controlled. In the preferred form illustrated, grinder motor 51 is a three-phase alternating current motor and is supplied with three-phase alternating electric current from power supply line 60, frequency converter 61, and grinder motor line 62. Speed control of grinder motor 51 is achieved by increasing or reducing the alternating current frequency by means of frequency converter 61, grinder motor speed being indirectly indicated by the alternating current frequency indicator 65.

It is also seen from the diagrammatic view of FIG. 5, that the'electric current drawn by grinder motor 51 through grinder motor line 62 passes through an ammeter 66. The current drawn by grinder'motor 51, and measured by ammeter 66, indirectly indicates the grinding loadat 67. As grinding pressure is increased on workpiece 50, the current detected by ammeter 66 increases, and vice versa.

During grinding, a liquid coolant is continuously sprayed on the surface of the workpiece 50 by a coolant nozzle 70, seen in FIG. 5. As already mentioned, the spraying of the coolant isconfined by the transparent plastic hood 15. Also, a metal shield 71 surrounds the chuck rotation zone 72 within which chuck 22 rotates. Coolant which is thrown from the chuck rotation zone 72 by centrifugal force is confined by shield 71, and recycled by conduit not shown to coolant reservoir 73. Micro switch 40 controls coolant circulation, in addition to controlling the reversing switch 36. An electrical signal from micro switch 40 through valve control line 75 controls coolant valve 76, through which valve a coolant pump 77 continuously circulates coolant from the coolant reservoir 73. When the grinding system 17 is lowered into. the grinding operation position indicated in FIGS. 1 and 5, valve 76 is positioned to deliver coolant through line 78 to nozzle 70. When the grinding system 17, is upwardly retracted, indicating the discontinuance of grinding, valve 76 shifts to recirculate the coolant to the coolant reservoir through recirculation line 79. As best seen in FIGS. 1

' and 3, the grinding wheel 52 is urged into grinding engagements with the workpiece 50 by the action of an actuator 80 upon theparallelogram linkage 18. In the preferred form of the invention illustrated, actuator 80 is a pneumatically cushioned hydraulic cylinder, comprised of an actuator cylinder 81, and actuator rod '82. The cylinder 81 is pivotally anchored by pivotal anchor 83 to the lower part of column 13, although it will be appreciated that any anchoring to the base structure 1 1 might be employed.

The upper end of the actuator rod 82 is pivotally connected by pivotal connection 85 to an arm 86 which extends from the parallelogram linkage 18.

The diagrammatic view of FIG. 5 shows the manner in which the operator can control the lowering or upward retraction of grinding system 17 by means of a continuously adjustable actuator control valve 90.

Valve 90 admits compressed air under pressure into the upper end of a reservoir 91. Compressed air supplied through line 92, regulator 93, pressure gauge 94, line 95, control valve 90, and line 96. Compressed air, indicated by the numeral 97, in the upper part of cylinder 91, expels oil, indicated by the numeral 98, in the lower part of cylinder 91 through grinding actuation line 100 and valve 101, communicating with the hydraulic cylinder 80, and causing it to urge the grinding system 17 into grinding operation against workpiece 50 through the mechanical connections already described.

A second cylinder 102, similar to cylinder 91, receives compressed air through line 103, pressure regulator 104, and pressure indicating gauge 105. Oil from cylinder 102 operates through actuator retracting openings in main column structure 130, permitting a small degree of positioning along a line through the axis of rotation of grinding system 17, by means of a toolmakers adjustment block 133, according to a construction well known in the toolmakers art.

Preferably column 13 is'slightly adjustable in position on chuck wall 23, by virtue of attaching bolts 135 received in slotted openings 136. Arcuate openings 136 are shown, although more restrictive movement might be achieved with longitudinal slots.

It is a preferred form of the invention that column 13 and parallelogram linkage 18 be connected by pairs of laterally spaced bearing members, and that both grindline 106, and valve 107, to cause actuator to .up-

wardly retractgrinding system 17, at all times except when the operator of the grinder 10 has rotated actuator control valve to apply sufficient pressure to lower the grinding system 17 into grinding engagement.

The resilient urging of actuator 80 to apply grinding load through the grinding system 17, .is opposed by a stop 110, which bears on a seat 111, which is in the form of an arm extending from parallelogram linkage 18.

The exact position of stop may be adjusted at all times, even during grinding, by means of a stop adjustment system indicated generally by the numeral 112, and comprised principally of a worm gear 113 and an adjustment wheel 114. Stop 110 is carried by worm gear 113, which is in turn anchored to column 13 by a rotatably mounted shaft 115.

A preferred construction for column 13 and parallelogram linkage 18 is shown in the illustrations, particularly in the perspective view of FIG. 3 and the exploded assembly of FIG. 4. Linkage 18 is seen to be comprised of an inboard swinging link 121, an outboard swinging link 122, and a longitudinally moving link 123. It will be seen that inboard link 121 carries the seat 111, upon which the stop 110 makes bearing engagement. Outboard link 122 carries the arm 86 through which the grinding load is applied by operation of actuator 80. Longitudinally movable link 123 provides the mounting platform 125 for the grinder system 17.

Column 13, which may be suitably constructed as a welded structure of massive steel plates, is comprised of two relatively adjustable parts, a main column structure 130, and an adjustable bearing support 131. Bearing support 131 is bolted to main column structure by bolts 132, which are received in slotted bolt ing load (applied by actuator 80) and adjustable stop resistance (applied by adjustable stop 110) be applied to the parallelogram linkage 18 between the laterally spaced bearing locations. 7

In the preferred form construction illustrated, the main column structure 130 is comprised principally of upright front and back sidewalls 136 and 137, a top 138, and transverse walls 139 and 139a. Sidewalls 136 and 137 are separated by a lateral spacing 140, which space apart inboard link bearings 141 and 142, and outboard link bearings 143 and 144.

Both actuator 80 and adjustable stop 110 are located in the lateral space 140 between the column sidewalls 136 and 137, and the bearings 141' and 143, at the front side, and bearings 142 and 144 at the back side of column 13.

The view of FIG. 2 reveals that the spaced bearings 141 to 144 permit precision adjustments; in FIG. 2 outboard link bearings 143 and 144 are partially sectioned to'reveal that they are preferably angle roller bearings as indicated at 145, and that, in bearing 144, slight tilting adjustments may be achieved on bearing 145 by adjustments in screws 146 on cap 147. It should also be noted that there is no through shaft, but that bearings 143 and 144 are independently seated in bearing support 131. 7

FIG. 2 also reveals that the actuator adjusting stop 115 is rotatably mounted in side members 136 and 137 V by bearings 148 and 149.

FIG. 2 also reveals that actuator cylinder pivotal mounting 83 is bolted to a cross member 150 extending between column sidewalls 136 and 137.

FIGS. 1, 3 and 4 illustrate the grinding platform 125,

and the manner in which the grinder motor 51 is mounted on .it. In the preferred form illustrated, the grinder platform 125 carries grinder motor 51 between laterally spaced inboard bearings 151 and 152, and outboard bearings 153 and 154, which are received in link 123at bearing recesses 151a to 154a, sequentially. It will be understood that bearings 151 to 154 are similar in construction to bearings 141 to 144, and like them have one bearing on each side adjustable for minor precision adjustments according to means familiar to those expert in precision tool construction.

Another adjustment is provided by the toolmakers adjustment block 155, which permits grinder motor 51 to be adjusted slightly along a line tangential to the rotation of grinder 51, thus providing a right angle complement to the adjustment permitted at adjustment block 133.

It is preferred construction that the parallelogram v linkage 18 have laterally spaced bearing locations and that the rotational axis of grinding system 17 is spaced between these locations and as near as possible to grinder platform 125. Thus, in the preferred construction for linkage 18, illustrated in the exploded assembly of FIG. 4, the longitudinal link is constructed to receive grinder motor 51 and grinding wheel 52 within a recess defined by the forwardly projecting bearing locations 151a to 1540.

FIG. 4 also shows certain other details of construction. Actuator arm 86 is seen to be bolted by bolts 160 to the upper surface of outboard link 122. Likewise, seat 11 1 is seen to be in the formof an arm attached by screws 161 to transverse member 162 of inboard link It will be noted that thelower part of longitudinally movable link 123 is notched at 165 to permit rotation of grinding wheel 52 in a location partially recessed between bearing locations 151a and 152a.

A sheet metal spatter shield 168 is positioned between front and back side members 136 and 137 to protect actuator 80 and the stop 110 from coolant oil thrown during grinding. Shield 168 is slotted at 169 to accommodate the movement of seat 111.

In operation, the workpiece 50 is placed in position with the grinding system 17 retracted into an upper position. Micro switch 40 detects this upwardly retracted position and consequently, the chuck 22 is stationary, and no coolant oil is permitted to flow from coolant nozzle 70. The operator switches chuck control valve 28 to the vacuum line 27, causing the workpiece 50 to be held by air pressure snugly in position on the upper surface 26 of chuck 22.

Once the workpiece 50 is in position, the operator moves actuator control'valve 90 to lower the grinding system 17 into grinding engagement with workpiece 50. The operator may leave the grinding motor 51 continuously running, even in retracted position, or may have a stop-and-start switch within his control, depending upon the preferences for a particular application.

As grinding system 17 moves into grinding engagement, micro switch 40 moves to cause the startup of coolant flow from nozzle 70, and to begin the rotation of chuck motor 21 and chuck 22.

As soon as grinding engagement occurs, the operator can detect the grinding load being applied, by reading the load indicating ammeter 65. He has three methods of load adjustment at his disposal, the application of pressure by actuator valve 90, the adjustment of grinder rotation speed by frequency converter 61, and the adjustment of the position of stop 110 by stop adjuster wheel 114. Preferably, the only adjustments required during the grinding operation of a single workpiece 50, or during the grinding of a succession of like workpieces, will be achieved by movement of stop adjustment wheel 114 to produce a predetermined grinding load indication at ammeter 66 and to maintain that grinding load for a period of time timed by timer clock 67.

It is a feature of novelty and an advantage of the grinder of the invention thata load-timed program can be predetermined with a few trial runs for achieving devices known to the automatic machine tool art.

It is an important feature of novelty and an advantage of the present invention that the operator of grinder 10 has the power to control the minute deformations and minute displacements which necessarily and inevitably occur in the present grinder as they do in all precision machines. The action of actuator 80 against stop 110 makes it possible for the operator to raise the opposing forces thus applied until all potentially harmful deformation and displacement have occurred, and all harmful tendency to vibrate has been eliminated, prior to the application of the critical grinding load to workpiece 50;

It will be obvious that the machine elements of grinder 10 are constructed as rigid as it is physically practical to make them. Also, bearings 141 to 144 and 151 to 154 are preloaded and adjusted and positioned under a substantial bearing load preliminary to any operating load, so that displacements are at a minimum. Nevertheless, some deformation and displacement are inevitable in the grinder 10, as in every tool, but they are brought under control by the means described.

It is an important feature of the grinder of the invention that its construction permits the achievement of two things not readily achieved by grinders heretofore known:

a. deformation and displacement of an imperfect machine maybe brought under control; and

b. a combination of controls on the forces in the grinder are available to an operator, so that precision grinding may be accomplished by following a predetermined grinding time-load program.

In the first place, the parallelogram linkage permits such adjustments and controls, not possible with other previously known systems employing parallel rotational axes for chuck and grinding wheel.

In the second place, the parallelogram linkage can be made to coact with an actuator system and an adjustable stop system which coact uniquely for both the aforementioned purposes (a) and (b).

In the grinder of the invention, grinding occurs on a workpiece surface at a grinding plane, while the workpiece, mounted on a rotating chuck, is rotated about the chuck axis. The planar end of grinding wheel 52 is applied only to a portion of the workpiece surface, lying within the grinding plane, referred to herein as the planar grinding area.

As the workpiece rotates with the chuck, the workpiece surface moves under the grinding wheel, and the planar grinding area produces a circumferential grinding path.

Persons skilled in this art recognize that a disk grinder of the type herein described can be operated to produce a great variety of grinding patterns, and a variety of these patterns are desired for different purposes, or to meet the specifications of different companies, or to accommodate different workpiece materials, or different grinding wheel compositions. It is, therefore, a valuable feature of the grinder of the present invention, that it has a diversity of controls which permit adaptation to achieve a variety of grinding patterns, and to arrive at substantially the same surface finish, with slight pattern variations, by delicate adjustments of different parts of the grinder.

In its preferred form, the grinder of the invention has great rigidity by virtue of the mechanical arrangement of the linkage column, and the relationship of that mechanical arrangement to the actuator and adjustable stop. It will be seen in the preferred form illustrated, that the column 13 is disposed along both sides of a linkage-movement plane, a vertical plane, normal to the grinding plane, and passing through the grinding axis of the grinding system 17. It is not necessary that the linkage-movement plane be parallel with a diameter of the chuck 26, on the contrary it will be recalled that the entire column 13 can be swiveled slightly by virtue of arcuate adjustment slot 136 (FIG. 3). Also, it is not necessarily true that the linkage-movement plane is directly down the center of column 13. However, it is much preferred that the column 13 and the entire parallelogram linkage 18, as well as the transverse spacing of its four pairs of bearings, be spaced more widely than the planar grinding area as viewed from the direction of column 13. Preferably, the virtues of rigidity are best realized if the width of the column, transverse to the linkage-movement plane, is not substantially less than the width of the planar grinding area, and preferably greater. It is further advantageous if the entire grinding system is nested into the parallelogram linkage toward the column 13, although physical construction problems usually permit only a slight nesting beyond the axis lines of the pivot points of longitudinally movable link 123.

lclaim:

l. A disk grinderfor grinding a workpiece surface in a grinding plane, said grinding being rotational about a grinding axis, said grinding being applied to a planar grinding area comprising only a portion of said workpiece surface, and said workpiece being rotated about a chuck axis parallel to said grinding axis during grinding to apply said planar grinding area to said workpiece surface in a circular grinding path, which grinder includes:

a chuck table;

a chuck system comprising:

a chuck motor mounted in said chuck table, and a chuck rotatably mounted in said chuck table and rotated about said chuck axis by said chuck motor, said chuck being adapted to hold and rotate said workpiece with said workpiece surface in said grinding plane, with a portion of said workpiece surface moving through said planar grinding area as said workpiece is rotated on said chuck axis;

a linkage support column adjacent said chuck, said column projecting outboard of said chuck and normal to said grinding plane, said column being disposed along both sides of a linkage movement plane through said grinding axis, and said column having a linkage-bearing plane disposed transver- 5 sely of said linkage-movement plane;

a parallelogram linkage pivotally mounted on said column to swing in said linkage movement plane, said linkage comprising:

a pair of swinging links pivotally attached to said column at said linkage-bearing plane, and including an inboard link and an outboard link, the latter being spaced farther outboard on said column than the former; and

a longitudinally movable link carried on the swinging ends of said pair of swinging links, said link having a line of movement adjacent to said grinding axis and normal to said grinding plane;

a grinder system mounted on said longitudinally movable link and comprising:

a grinder motor, and

a grinding wheel driven by said grinding motor to rotate about said grinding axis, said grinding wheel having a planar grinding end to make grinding engagement with a portion of said workpiece surface defined by said planar grinding area; and

a grinding load system controllably urging said grinding wheel into grinding engagement with said workpiece surface.

2. A disk grinder as described in claim 1 in which said grinding load system comprises:

a grinding load actuator adapted to urge said grinding wheel into grinding engagement with said workpiece surface; and

an adjustable stop means for opposing the movement urged by said actuator.

3. A disk grinder as described in claim 1 in which said grinding load system includes:

a grinding load actuator adapted to urge said grinding wheel into grinding engagement with a workpiece surface;

an adjustable stop means for opposing the movement 45 urged by said grinding load actuator;

grinding load indicator means; and

stop adjuster means for continuously altering said adjustable stop during grinding operation, to achieve a predetermined grinding program.

4. A disk grinder as described in claim 1 in which said parallelogram linkage is pivoted, on at least one of its axes, on a pair of bearings, one disposed on each side of said linkage movement plane, said bearings being spaced from each other transversely of said link- 55 age movement plane an axial distance not substantially less than the projection on an axial line between said bearings of a parallel line within said planar grinding area.

5. A disk grinder as described in claim 1 in which 60 said column and the links of said parallelogram linkage have a transverse extent on each side of said linkage movement plane, not substantially less than the transverse extent of said planar grinding area on the corresponding side of said linkage movement plane.

6. A disk grinder as described in claim 5 in which said parallelogram linkage is pivoted at each of its four pivot axes on a pair of bearings, the bearings of each pair being spaced from each other an axial distance transverse of said linkage movement plane not substantially less than the transverse extent of said planar grinding area on the corresponding side of said linkage movement plane.

7. A disk grinder as described in claim 6 in which said longitudinally movable link is formed to receive said grinding system at least partly between thepivot axes of said longitudinally movable link and said linkage-bearing plane. I

8. A disk grinder as described in claim 1 in which said column is a hollow structure comprising a pair of sidewalls, each of said sidewalls being spaced transversely from said linkage-movement plane a distance not substantially less than the transverse extent of said planar grinding area on the same side of said linkagemovement plane; and

said grinding load system comprises:

an actuator accommodated between the spaced sidewalls of said column, and actingupon said grinding system through said linkage to urge said grinding wheel into' grinding engagement with said workpiece surface;

a stop means also positioned between said spaced sidewalls of said column; 1

bumper means on said parallelogram linkage engaged by said stop means to resist the movement urged by said actuator; and

stop adjustment means for controllably positioning said stop.

9. A disk grinder as described in claim 1 in which said chuck motor and said chuck rotate as a unit on a common chuck axis.

10. Adisk grinder as described in claim 9 in which said chuck motor and said chuck rotate on a common hollow shaft assembly, and said chuck system includes:

Walls defining air passages to the surface of said chuck receiving said workpiece; and

Selectively controllable air pressure and vacuum means communicating with said hollow shaft system for selectively retaining a workpiece on said chuck by vacuum, or displacing it therefrom by air pressure.

11. A disk grinder for grinding a workpiece surface in a grinding plane, said grinding being rotational about a grinding axis, said grinding being applied to a planar grinding area comprising only a portion of said workpiece surface, and said workpiece being rotated about a chuck axis parallel to said grinding axis during grinding to apply said planar grinding area to said workpiece surface in a circular grinding path, which grinder includes:

va chuck table;

a chuck system comprising:

a chuck motor mounted in said chuck table, and a chuck rotatably mounted in said chuck table and rotated about said chuck axis by said chuck motor, said chuck being adapted to hold and rotate said workpiece with said workpiece surface in said grinding plane, with a portion of said workpiece surface moving through said planar grinding area as said workpiece is rotated on said chuck axis;

a linkage support column adjacent said chuck, said column projecting outboard of said chuck and normal to said grinding plane, said column being disposed along both sides of a linkage movement plane through said grinding'axis, and said column having a linkage-bearing plane disposed transversely of said linkage-movement plane; said column comprising:

a pair of sidewalls substantially parallel to said linkage-movement plane, and including an operator sidewall and a back-sidewall, on opposite sides of said plane; and

transverse wall structure extending between said sidewalls;

an outboard bearing platform mounted on the outboard end of said column and longitudinally adjustable on said column in a direction parallel with said linkage-movement plane;

a parallelogram linkage pivotally mounted on said column and said outboard bearing platform to swing in said linkage-movement plane, said linkage comprising:

a pair of swinging links, including an inboard link pivoted to said column at two points, one in each of said-column sidewalls; and an outboard link pivoted to said outboard bearing platform at two pivot points spaced transversely of said linkage-movement plane on opposite sides thereof; and

a longitudinally movable link pivoted at an outboard end to said outboard link at two pivot points spaced transversely of said linkage-movement plane, and at its inboard end pivoted to said inboard link at two pivot points spaced transversely of said linkage-movement plane, said longitudinally movable l-ink having a line of movement adjacent to said grinding axis and normal to said grinding plane;

grinder system mounted on said longitudinally movable link between planes spaced closer to said a grinding load system controllably urging said grinding wheel into grinding engagement with said workpiece surface, said system comprising: a double-acting actuator between said column sidewalls, and connected to said parallelogram linkage, said actuator operating in a retraction direction to retract said grinding system from said workpiece surface, and in a grinding direction to urge said grinding wheel into contact with said workpiece surface; and

a stop means mounted between said sidewalls of said column, and engaging said parallelogram linkage, to stop the movement of said grinding system into grinding engagement with said workpiece surface, at a predetermined stop position; and

stop adjustment means for changing the position of said stop to correspond to different grinding plane locations; and grinding load indicator means for indicating grinding load being applied by said grinder system to said workpiece surface. 12. A disk grinder as described in claim 11 in which said double-acting actuator is a hydraulic cylinder, and pressure on the hydraulic liquid operating said cylinder is applied through the medium of a resiliently compressible gas, and said grinder includes operating means for controlling the pressure of said gas, whereby combinations of adjustment of said stop and control of the pressure of said actuator during grinding operation can be used in opposition to control deformation and displacement in said disk grinder.

13. A disk grinder as described in claim 11 inwhich said stop adjustment means comprises a right-angle, reduction-gear means, rotatably mounted between said operator sidewall and said back sidewall, and said stop adjustment means includes a control wheel means exterior to said column adjacent said operator sidewall.

14. A disk grinder as described in claim 11 in which said grinding system is at least partly nested between the operator side pivots and the back side pivots of said longitudinally movable link.

15. A disk grinder as described in claim 11 in which each of the four pivot axes of said parallelogram linkage is provided with a pair of pivot bearings, one on the operator side of said linkage-movement plane, and one on the back side of said linkage-movement plane; and one bearing of at least one of those pairs of bearings is adjustable in position with respect to the other bearing.

16. A disk grinder for grinding a workpiece surface in a grinding plane, said grinding being rotational about a grinding axis, said grinding being applied to a planar grinding area, comprising only a portion of said workpiece surface, and said workpiece being rotated about a chuck axis parallel to said grinding axis during grinding to apply said planar grinding area to said workpiece surface in a circular grinding path, which grinder includes:

a chuck table; a chuck system mounted in said chuck table, said chuck system comprising a chuck motor, a chuck, and a chuck shaft system rotating as a unit about said chuck axis, said chick system further includmg: an electrical reversing switch controlling electric power supplied to said chuck motor, said switch having a grinding position for driving said motor in an operating direction desired during grinding, and a stopping position for delivering current to said motor to resist rotation in the operating direction; and

a rotation sensing means for sensing the rotation of said chuck system, and coacting with said reversing switch when said switch is in said stopping position, to apply stopping current through said reversing switch to bring said chuck system to a stop;

a linkage support column adjacent said chuck, said column projecting outboard of said chuck and normal to said grinding plane, said column being disposed along both sides of a linkage-movement plane through said grinding axis, and said column having a linkage-bearing plane disposed transversely of said linkage-movement plane;

a parallelogram linkage pivotally mounted on said column to swing in said linkage-movement plane, said linkage comprising:

a pair of swinging links pivotally attached to said column at said linkage-bearing plane, and including an inboard link and an outboard link, the latter being spaced farther outboard on said column than the former; and

a longitudinally movable link carried on the swinging ends of said pair of swinging links, said link I having a line of movement adjacent to said grinding axis and normal to said grinding plane;

a grinder system mounted on said longitudinally movable link and comprising:

a grinder motor, and

a grinding wheel driven by said grinder motor to rotate about said grinding axis, said grinding wheel having a planar grinding end to make grinding engagement with a portion of said workpiece surface defined by said planar grinding area; and

a grinding load system controllably urging said grinding wheel into grinding engagement with said workpiece surface.

17. A disk grinder as described in claim 16 which in cludes a grinding position sensing means, which places said reversing switch in operating position when said grinding system is in position to bring said grinding wheel into grinding engagement with said workpiece surface; and said grinding position sensing means shifting said reversing switch to said stopping position when said grinding system is retracted from grinding engagement with said workpiece surface.

18. A disk grinder for grinding a workpiece surface in a grinding plane, said grinding being rotational about a grinding axis, said grinding being applied to a planar grinding area comprising only a portion of said workpiece surface, and said workpiece being rotated about a chuck axis parallel to said grinding axis during grinding to apply said planar grinding area to said workpiece surface in a circular grinding path, which grinder includes:

a chuck table;

a chuck system comprising:

a chuck motor mounted in said chuck table, and

a chuck rotatably mounted in said chuck table and rotated about said chuck axis by said chuck motor, said chuck being adapted to hold and rotate said workpiece with said workpiece surface in said grinding plane, with a portion of said workpiece surface moving through said planar grinding area as said workpiece is rotated on said chuck axis/ a linkage support column adjacent said chuck, said column projecting outboard of said chuck and normal to said grinding plane, said column being disposed along both sides of a linkage-movement plane through said grinding axis, and said column having a linkage-bearing plane disposed transversely of said linkage-movement plane;

a parallelogram linkage pivotally mounted on said column to swing in said linkage-movement plane, said linkage comprising:

a pair of swing links pivotally attached to said resiliently cushioned by gas and controllable to a column at said linkage-bearing plane, and inpredetermined pressure;

cluding an inboard link and an outboard link, grinding load control means for operating said acthe latter being spaced farther outboard on said tuator in a direction to apply said grinding wheel column than the former; and to said workpiece surface;

a longitudinally movable link carried on the swingretraction control means for operation of said acing ends of said pair of swinging links, said link tuator to retract said grinding system from said having a line of movement adjacent to said w rkp e S and grinding axis and normal to said grinding plane; adju le stop m ans for pposing the operation a grinder system mounted on said longitudinally of said t a in a grinding 108d pp y movable link and comprising: direction, when said grinding wheel reaches a a grinder motor, and predetermined grinding plane.

a i di g h l d i b id i di motor 19. A disk grinder as described in claim 18, in which rotate about said grinding axi id i di said chuck motor is an alternating current motor, and wheel having a planar grinding end to make in which Said dlsk gflndel'mcludesi grinding engagement with a portion f i afrequency changer system in the electrical current workpiece surface defined by said planar grind- Supply to 531d chuck motor, w f y to control i ing area; d rotational speed of said grinding wheel during a grinding load system controllably urging said grindgrmdmg;

i h i di engagement with Said 20 a current indicating means associated with said workpiece surface, said grinding system comp chuck motorfor cont nuously indicating the grindi ing load applied by said grinder; and a d b| i hydraulic cylinder actuator means for the operator to establish combinations of mounted in said column and engaging said Stop l f i actuator Pressure, and gflnfimg parallelogram linkage; adjustable pneumatic wheel rotation to conform to a predetermined pressure means for supplying hydraulic fluid to grmdmg Pmgramsaid hydraulic cylinder under a pressure 

1. A disk grinder for grinding a workpiece surface in a grinding plane, said grinding being rotational about a grinding axis, said grinding being applied to a planar grinding area comprising only a portion of said workpiece surface, and said workpiece being rotated about a chuck axis parallel to said grinding axis during grinding to apply said planar grinding area to said workpiece surface in a circular grinding path, which grinder includes: a chuck table; a chuck system comprising: a chuck motor mounted in said chuck table, and a chuck rotatably mounted in said chuck table and rotated about said chuck axis by said chuck motor, said chuck being adapted to hold and rotate said workpiece with said workpiece surface in said grinding plane, with a portion of said workpiece surface moving through said planar grinding area as said workpiece is rotated on said chuck axis; a linkage support column adjacent said chuck, said column projecting outboard of said chuck and normal to said grinding plane, said column being disposed along both sides of a linkage movement plane through said grinding axis, and said column having a linkage-bearing plane disposed transversely of said linkage-movement plane; a parallelogram linkage piVotally mounted on said column to swing in said linkage movement plane, said linkage comprising: a pair of swinging links pivotally attached to said column at said linkage-bearing plane, and including an inboard link and an outboard link, the latter being spaced farther outboard on said column than the former; and a longitudinally movable link carried on the swinging ends of said pair of swinging links, said link having a line of movement adjacent to said grinding axis and normal to said grinding plane; a grinder system mounted on said longitudinally movable link and comprising: a grinder motor, and a grinding wheel driven by said grinding motor to rotate about said grinding axis, said grinding wheel having a planar grinding end to make grinding engagement with a portion of said workpiece surface defined by said planar grinding area; and a grinding load system controllably urging said grinding wheel into grinding engagement with said workpiece surface.
 2. A disk grinder as described in claim 1 in which said grinding load system comprises: a grinding load actuator adapted to urge said grinding wheel into grinding engagement with said workpiece surface; and an adjustable stop means for opposing the movement urged by said actuator.
 3. A disk grinder as described in claim 1 in which said grinding load system includes: a grinding load actuator adapted to urge said grinding wheel into grinding engagement with a workpiece surface; an adjustable stop means for opposing the movement urged by said grinding load actuator; grinding load indicator means; and stop adjuster means for continuously altering said adjustable stop during grinding operation, to achieve a predetermined grinding program.
 4. A disk grinder as described in claim 1 in which said parallelogram linkage is pivoted, on at least one of its axes, on a pair of bearings, one disposed on each side of said linkage movement plane, said bearings being spaced from each other transversely of said linkage movement plane an axial distance not substantially less than the projection on an axial line between said bearings of a parallel line within said planar grinding area.
 5. A disk grinder as described in claim 1 in which said column and the links of said parallelogram linkage have a transverse extent on each side of said linkage movement plane, not substantially less than the transverse extent of said planar grinding area on the corresponding side of said linkage movement plane.
 6. A disk grinder as described in claim 5 in which said parallelogram linkage is pivoted at each of its four pivot axes on a pair of bearings, the bearings of each pair being spaced from each other an axial distance transverse of said linkage movement plane not substantially less than the transverse extent of said planar grinding area on the corresponding side of said linkage movement plane.
 7. A disk grinder as described in claim 6 in which said longitudinally movable link is formed to receive said grinding system at least partly between the pivot axes of said longitudinally movable link and said linkage-bearing plane.
 8. A disk grinder as described in claim 1 in which said column is a hollow structure comprising a pair of sidewalls, each of said sidewalls being spaced transversely from said linkage-movement plane a distance not substantially less than the transverse extent of said planar grinding area on the same side of said linkage-movement plane; and said grinding load system comprises: an actuator accommodated between the spaced sidewalls of said column, and acting upon said grinding system through said linkage to urge said grinding wheel into grinding engagement with said workpiece surface; a stop means also positioned between said spaced sidewalls of said column; bumper means on said parallelogram linkage engaged by said stop means to resist the movement urged by said actuator; and stop adjustment means for controllably positioning said stOp.
 9. A disk grinder as described in claim 1 in which said chuck motor and said chuck rotate as a unit on a common chuck axis.
 10. A disk grinder as described in claim 9 in which said chuck motor and said chuck rotate on a common hollow shaft assembly, and said chuck system includes: Walls defining air passages to the surface of said chuck receiving said workpiece; and Selectively controllable air pressure and vacuum means communicating with said hollow shaft system for selectively retaining a workpiece on said chuck by vacuum, or displacing it therefrom by air pressure.
 11. A disk grinder for grinding a workpiece surface in a grinding plane, said grinding being rotational about a grinding axis, said grinding being applied to a planar grinding area comprising only a portion of said workpiece surface, and said workpiece being rotated about a chuck axis parallel to said grinding axis during grinding to apply said planar grinding area to said workpiece surface in a circular grinding path, which grinder includes: a chuck table; a chuck system comprising: a chuck motor mounted in said chuck table, and a chuck rotatably mounted in said chuck table and rotated about said chuck axis by said chuck motor, said chuck being adapted to hold and rotate said workpiece with said workpiece surface in said grinding plane, with a portion of said workpiece surface moving through said planar grinding area as said workpiece is rotated on said chuck axis; a linkage support column adjacent said chuck, said column projecting outboard of said chuck and normal to said grinding plane, said column being disposed along both sides of a linkage movement plane through said grinding axis, and said column having a linkage-bearing plane disposed transversely of said linkage-movement plane; said column comprising: a pair of sidewalls substantially parallel to said linkage-movement plane, and including an operator sidewall and a back sidewall, on opposite sides of said plane; and transverse wall structure extending between said sidewalls; an outboard bearing platform mounted on the outboard end of said column and longitudinally adjustable on said column in a direction parallel with said linkage-movement plane; a parallelogram linkage pivotally mounted on said column and said outboard bearing platform to swing in said linkage-movement plane, said linkage comprising: a pair of swinging links, including an inboard link pivoted to said column at two points, one in each of said column sidewalls; and an outboard link pivoted to said outboard bearing platform at two pivot points spaced transversely of said linkage-movement plane on opposite sides thereof; and a longitudinally movable link pivoted at an outboard end to said outboard link at two pivot points spaced transversely of said linkage-movement plane, and at its inboard end pivoted to said inboard link at two pivot points spaced transversely of said linkage-movement plane, said longitudinally movable link having a line of movement adjacent to said grinding axis and normal to said grinding plane; a grinder system mounted on said longitudinally movable link between planes spaced closer to said linkage-movement plane than the pivot points of said parallelogram linkage, said grinder system comprising: a grinder motor mounted on said longitudinally movable link, said motor including a grinder motor shaft rotating coaxially with said grinding axis; a grinding wheel mounted on the inboard end of said motor shaft, said grinding wheel having a planar grinding end to make grinding engagement with a portion of said workpiece at said planar brinding area; and a grinding load system controllably urging said grinding wheel into grinding engagement with said workpiece surface, said system comprising: a double-acting actuator between said column sidewalls, and connected to said parallelogram linkage, said actuator operating in a retraction direction to retract said grinding System from said workpiece surface, and in a grinding direction to urge said grinding wheel into contact with said workpiece surface; and a stop means mounted between said sidewalls of said column, and engaging said parallelogram linkage, to stop the movement of said grinding system into grinding engagement with said workpiece surface, at a predetermined stop position; and stop adjustment means for changing the position of said stop to correspond to different grinding plane locations; and grinding load indicator means for indicating grinding load being applied by said grinder system to said workpiece surface.
 12. A disk grinder as described in claim 11 in which said double-acting actuator is a hydraulic cylinder, and pressure on the hydraulic liquid operating said cylinder is applied through the medium of a resiliently compressible gas, and said grinder includes operating means for controlling the pressure of said gas, whereby combinations of adjustment of said stop and control of the pressure of said actuator during grinding operation can be used in opposition to control deformation and displacement in said disk grinder.
 13. A disk grinder as described in claim 11 in which said stop adjustment means comprises a right-angle, reduction-gear means, rotatably mounted between said operator sidewall and said back sidewall, and said stop adjustment means includes a control wheel means exterior to said column adjacent said operator sidewall.
 14. A disk grinder as described in claim 11 in which said grinding system is at least partly nested between the operator side pivots and the back side pivots of said longitudinally movable link.
 15. A disk grinder as described in claim 11 in which each of the four pivot axes of said parallelogram linkage is provided with a pair of pivot bearings, one on the operator side of said linkage-movement plane, and one on the back side of said linkage-movement plane; and one bearing of at least one of those pairs of bearings is adjustable in position with respect to the other bearing.
 16. A disk grinder for grinding a workpiece surface in a grinding plane, said grinding being rotational about a grinding axis, said grinding being applied to a planar grinding area, comprising only a portion of said workpiece surface, and said workpiece being rotated about a chuck axis parallel to said grinding axis during grinding to apply said planar grinding area to said workpiece surface in a circular grinding path, which grinder includes: a chuck table; a chuck system mounted in said chuck table, said chuck system comprising a chuck motor, a chuck, and a chuck shaft system rotating as a unit about said chuck axis, said chick system further including: an electrical reversing switch controlling electric power supplied to said chuck motor, said switch having a grinding position for driving said motor in an operating direction desired during grinding, and a stopping position for delivering current to said motor to resist rotation in the operating direction; and a rotation sensing means for sensing the rotation of said chuck system, and coacting with said reversing switch when said switch is in said stopping position, to apply stopping current through said reversing switch to bring said chuck system to a stop; a linkage support column adjacent said chuck, said column projecting outboard of said chuck and normal to said grinding plane, said column being disposed along both sides of a linkage-movement plane through said grinding axis, and said column having a linkage-bearing plane disposed transversely of said linkage-movement plane; a parallelogram linkage pivotally mounted on said column to swing in said linkage-movement plane, said linkage comprising: a pair of swinging links pivotally attached to said column at said linkage-bearing plane, and including an inboard link and an outboard link, the latter being spaced farther outboard on said column than the former; and a longitudinally movable link Carried on the swinging ends of said pair of swinging links, said link having a line of movement adjacent to said grinding axis and normal to said grinding plane; a grinder system mounted on said longitudinally movable link and comprising: a grinder motor, and a grinding wheel driven by said grinder motor to rotate about said grinding axis, said grinding wheel having a planar grinding end to make grinding engagement with a portion of said workpiece surface defined by said planar grinding area; and a grinding load system controllably urging said grinding wheel into grinding engagement with said workpiece surface.
 17. A disk grinder as described in claim 16 which includes a grinding position sensing means, which places said reversing switch in operating position when said grinding system is in position to bring said grinding wheel into grinding engagement with said workpiece surface; and said grinding position sensing means shifting said reversing switch to said stopping position when said grinding system is retracted from grinding engagement with said workpiece surface.
 18. A disk grinder for grinding a workpiece surface in a grinding plane, said grinding being rotational about a grinding axis, said grinding being applied to a planar grinding area comprising only a portion of said workpiece surface, and said workpiece being rotated about a chuck axis parallel to said grinding axis during grinding to apply said planar grinding area to said workpiece surface in a circular grinding path, which grinder includes: a chuck table; a chuck system comprising: a chuck motor mounted in said chuck table, and a chuck rotatably mounted in said chuck table and rotated about said chuck axis by said chuck motor, said chuck being adapted to hold and rotate said workpiece with said workpiece surface in said grinding plane, with a portion of said workpiece surface moving through said planar grinding area as said workpiece is rotated on said chuck axis/ a linkage support column adjacent said chuck, said column projecting outboard of said chuck and normal to said grinding plane, said column being disposed along both sides of a linkage-movement plane through said grinding axis, and said column having a linkage-bearing plane disposed transversely of said linkage-movement plane; a parallelogram linkage pivotally mounted on said column to swing in said linkage-movement plane, said linkage comprising: a pair of swing links pivotally attached to said column at said linkage-bearing plane, and including an inboard link and an outboard link, the latter being spaced farther outboard on said column than the former; and a longitudinally movable link carried on the swinging ends of said pair of swinging links, said link having a line of movement adjacent to said grinding axis and normal to said grinding plane; a grinder system mounted on said longitudinally movable link and comprising: a grinder motor, and a grinding wheel driven by said grinding motor to rotate about said grinding axis, said grinding wheel having a planar grinding end to make grinding engagement with a portion of said workpiece surface defined by said planar grinding area; and a grinding load system controllably urging said grinding wheel into grinding engagement with said workpiece surface, said grinding system comprising: a double-acting hydraulic cylinder actuator mounted in said column and engaging said parallelogram linkage; adjustable pneumatic pressure means for supplying hydraulic fluid to said hydraulic cylinder under a pressure resiliently cushioned by gas and controllable to a predetermined pressure; grinding load control means for operating said actuator in a direction to apply said grinding wheel to said workpiece surface; retraction control means for operation of said actuator to retract said grinding system from said workpiece surface; and adjustable stop means for opposing the operation of said actuator in a griNding load applying direction, when said grinding wheel reaches a predetermined grinding plane.
 19. A disk grinder as described in claim 18, in which said chuck motor is an alternating current motor, and in which said disk grinder includes: a frequency changer system in the electrical current supply to said chuck motor, whereby to control the rotational speed of said grinding wheel during grinding; a current indicating means associated with said chuck motor for continuously indicating the grinding load applied by said grinder; and means for the operator to establish combinations of stop adjustment, actuator pressure, and grinding wheel rotation to conform to a predetermined grinding program. 